Constitutive activity of NF-kappa B in myeloid cells drives pathogenicity of monocytes and macrophages during autoimmune neuroinflammation

The NF-κB/REL-family of transcription factors plays a central role in coordinating the expression of a wide variety of genes controlling immune responses including autoimmunity of the central nervous system (CNS). The inactive form of NF-κB consists of a heterodimer which is complexed with its inhibitor, IκB. Conditional knockout-mice for IκBα in myeloid cells (lysMCreIκBα^fl/fl) have been generated and are characterized by a constitutive activation of NF-κB proteins allowing the study of this transcription factor in myelin-oligodendrocyte-glycoprotein induced experimental autoimmune encephalomyelitis (MOG-EAE), a well established experimental model for autoimmune demyelination of the CNS.

In comparison to controls, lysMCreIκBα^fl/fl mice developed a more severe clinical course of EAE. Upon histological analysis on day 15 p.i., there was an over two fold increased infiltration of T-cells and macrophages/microglia. In addition, lysMCreIκBα^fl/fl mice displayed an increased expression of the NF-κB dependent factor inducible nitric oxide synthase in inflamed lesions. These changes in the CNS are associated with increased numbers of CD11b positive splenocytes and a higher expression of Ly6c on monocytes in the periphery. Well in accordance with these changes in the myeloid cell compartment, there was an increased production of the monocyte cytokines interleukin(IL)-12 p70, IL-6 and IL-1beta in splenocytes. In contrast, production of the T-cell associated cytokines interferon gamma (IFN-gamma) and IL-17 was not influenced.

In summary, myeloid cell derived NF-κB plays a crucial role in autoimmune inflammation of the CNS and drives a pathogenic role of monocytes and macrophages independently from T-cells.

Modulation of autoimmune demyelination by laquinimod via induction of brain-derived neurotrophic factor

Laquinimod is a promising, orally available compound that has been successfully evaluated in placebo-controlled phase II/III studies of relapsing-remitting multiple sclerosis (MS). Studies are ongoing to further define laquinimod's modulatory mechanisms. Analyses in the animal model of experimental autoimmune encephalomyelitis (EAE) demonstrate that laquinimod reduces infiltration of leukocytes into the central nervous system, induces a Th1 to Th2/3 shift, and suppresses Th17 responses. To evaluate the potential neuroprotective capacity of laquinimod via modulation of brain-derived neurotrophic factor (BDNF), we analyzed the expression of BDNF in blood samples from 203 MS patients treated with laquinimod. Furthermore, we investigated the effect of laquinimod in EAE using a conditional BDNF knockout strain lacking BDNF expression in myeloid cells and T cells (LLF mice). Treatment with laquinimod resulted in a significant and persistent increase in BDNF serum levels of MS patients when compared to baseline and placebo-treated patients. LLF mice treated with laquinimod display a more severe EAE disease course in comparison to wild-type mice. Furthermore, laquinimod-treated wild-type monocytes secreted an anti-inflammatory cytokine pattern in comparison to untreated wild-type monocytes and treated LLF monocytes. Adoptive transfer of laquinimod stimulated monocytes into mice with EAE ameliorated the disease course. Consistent with immunomodulatory properties, laquinimod skewed monocytes toward a regulatory phenotype and also acted via modulation of BDNF, which may contribute to neuroprotection in MS patients.

Fumaric acid esters exert neuroprotective effects in neuroinflammation via activation of the Nrf2 antioxidant pathway

Inflammation and oxidative stress are thought to promote tissue damage in multiple sclerosis. Thus, novel therapeutics enhancing cellular resistance to free radicals could prove useful for multiple sclerosis treatment. BG00012 is an oral formulation of dimethylfumarate. In a phase II multiple sclerosis trial, BG00012 demonstrated beneficial effects on relapse rate and magnetic resonance imaging markers indicative of inflammation as well as axonal destruction. First we have studied effects of dimethylfumarate on the disease course, central nervous system, tissue integrity and the molecular mechanism of action in an animal model of chronic multiple sclerosis: myelin oligodendrocyte glycoprotein induced experimental autoimmune encephalomyelitis in C57BL/6 mice. In the chronic phase of experimental autoimmune encephalomyelitis, preventive or therapeutic application of dimethylfumarate ameliorated the disease course and improved preservation of myelin, axons and neurons. In vitro, the application of fumarates increased murine neuronal survival and protected human or rodent astrocytes against oxidative stress. Application of dimethylfumarate led to stabilization of the transcription factor nuclear factor (erythroid-derived 2)-related factor 2, activation of nuclear factor (erythroid-derived 2)-related factor 2-dependent transcriptional activity and accumulation of NADP(H) quinoline oxidoreductase-1 as a prototypical target gene. Furthermore, the immediate metabolite of dimethylfumarate, monomethylfumarate, leads to direct modification of the inhibitor of nuclear factor (erythroid-derived 2)-related factor 2, Kelch-like ECH-associated protein 1, at cysteine residue 151. In turn, increased levels of nuclear factor (erythroid-derived 2)-related factor 2 and reduced protein nitrosylation were detected in the central nervous sytem of dimethylfumarate-treated mice. Nuclear factor (erythroid-derived 2)-related factor 2 was also upregulated in the spinal cord of autopsy specimens from untreated patients with multiple sclerosis. In dimethylfumarate-treated mice suffering from experimental autoimmune encephalomyelitis, increased immunoreactivity for nuclear factor (erythroid-derived 2)-related factor 2 was detected by confocal microscopy in neurons of the motor cortex and the brainstem as well as in oligodendrocytes and astrocytes. In mice deficient for nuclear factor (erythroid-derived 2)-related factor 2 on the same genetic background, the dimethylfumarate mediated beneficial effects on clinical course, axon preservation and astrocyte activation were almost completely abolished thus proving the functional relevance of this transcription factor for the neuroprotective mechanism of action. We conclude that the ability of dimethylfumarate to activate nuclear factor (erythroid-derived 2)-related factor 2 may offer a novel cytoprotective modality that further augments the natural antioxidant responses in multiple sclerosis tissue and is not yet targeted by other multiple sclerosis therapies.

Efficacy of fumaric acid esters in the R6/2 and YAC128 models of Huntington's disease

Huntington's disease (HD) is an autosomal dominantly inherited progressive neurodegenerative disease. The exact sequel of events finally resulting in neurodegeneration is only partially understood and there is no established protective treatment so far. Some lines of evidence speak for the contribution of oxidative stress to neuronal tissue damage. The fumaric acid ester dimethylfumarate (DMF) is a new disease modifying therapy currently in phase III studies for relapsing-remitting multiple sclerosis. DMF potentially exerts neuroprotective effects via induction of the transcription factor “nuclear factor E2-related factor 2” (Nrf2) and detoxification pathways. Thus, we investigated here the therapeutic efficacy of DMF in R6/2 and YAC128 HD transgenic mice which mimic many aspects of HD and are characterized by an enhanced generation of free radicals in neurons. Treatment with DMF significantly prevented weight loss in R6/2 mice between postnatal days 80–90. At the same time, DMF treatment led to an attenuated motor impairment as measured by the clasping score. Average survival in the DMF group was 100.5 days vs. 94.0 days in the placebo group. In the histological analysis on day 80, DMF treatment resulted in a significant preservation of morphologically intact neurons in the striatum as well as in the motor cortex. DMF treatment resulted in an increased Nrf2 immunoreactivity in neuronal subpopulations, but not in astrocytes. These beneficial effects were corroborated in YAC128 mice which, after one year of DMF treatment, also displayed reduced dyskinesia as well as a preservation of neurons. In conclusion, DMF may exert beneficial effects in mouse models of HD. Given its excellent side effect profile, further studies with DMF as new therapeutic approach in HD and other neurodegenerative diseases are warranted.

[Rituximab in treatment for neuroimmunological diseases]

Rituximab, a human-mouse chimeric CD20 monoclonal antibody that depletes CD20-positive B cells, has already demonstrated efficacy in hematologic and rheumatologic diseases. Treatment with rituximab results in depletion of CD20-positive cells via multiple mechanisms, including complement-mediated or antibody-dependent cytotoxicity and apoptosis. Recent histopathologic and immunologic studies reveal an influence of B cells on the development and perpetuation of many chronic inflammatory diseases of the nervous system. Promising results with rituximab were already reported in the therapy of myasthenia gravis, immunoneuropathies, neuromyelitis optica, and multiple sclerosis, in which first controlled studies have been recently published. In this review we summarize available data from these reports and also discuss possible underlying molecular mechanisms.

Deep brain stimulation improves performance of complex instrumental paradigms

Patients with Parkinson's disease (PD) show deficits of motion behaviour and cognitive function, which were assessed with various instrumental paradigms. Objectives of the present trial were to investigate the effects of bilateral deep brain stimulation (DBS) of the subthalamic nucleus (STN) on the performance of complex and simple movement series, on the execution of simple reaction time (SRT) paradigms following an acoustic or a visual stimulus, on scored motor symptoms and the interrelation of the various study parameters in PD patients. Motor symptoms, operation of complex movements, and the execution of SRT tasks significantly improved when the stimulator was switched on. Execution of simple movement series did not differ between the on and off conditions of the stimulator. Instrumental test results significantly correlated with scored motor symptoms in particular during the off condition. During the on state, significant correlations were found between the performance of complex motion sequences and the SRT outcomes. PD patients treated with DBS of the STN show better results for more complex instrumental paradigms with a higher need for cognitive effort during the on situation due to improvements in motor performance, function of the basal ganglia-thalamocortical circuitry and cognitive function.

Dyskinesien bei Morbus Parkinson - Klinik, Ätiologie, Therapie

Parkinson's disease (PD), a slowly, progressive degenerative disorder of the central nervous system, which affects about ten million people world-wide, is currently treated symptomatically. Current treatment aim i. e. to balance the decreased dopamine turnover in striatal neurons. Chronic exposure to dopaminergic agents, however, supports onset of motor complications and dyskinesia in the long term. Dyskinesia appear mainly as chorea, athetosis, dystonia, stereotypia, ballism or a combination. Sometimes excessive abnormal facial, body and limb movements depend on the overall dosage of dopaminergic substitution. This is why the main therapy is based on reducing the total dosage of dopaminergic substances. Either alternative or additional well-tried substances like apomorphine, amantadine or clozapine are used. New possibilities in treatment emerge from substances like sarizotan, istradefylline, fipampezol or talampanel. Even so disability and reduced quality of life in PD patients and their caregivers may exist. This survey describes the major clinical features, aetiology and demographics of treatment-associated dyskinesia in PD.